Treating casein plastics



Patented Dec. 28, 1937 UNITED STATES mosses "PATENT orrlfes 2,103,993 TREATING CASEIN PLASTICS Will E. Vawt er, Bainbridge, N.- 31., assignor to American Plastics Corporation, .New York, N. Y., a corporation of New York 7 No Drawing. Application October 6, I936,

' Serial No. 104,299

5 Claims. (01. 18-475) This invention has for its object an improvement in theso-calledchemical finishing and.

polishing of shaped objects made from casein plastics, including buttons, blanks, beads, buckles and various others. .The art'of making casein plastics is so well known that it is not necessary to review the processin this case. After the shaped casein objects have been made by the usual method including the treatment to toughen ivory nut button art. Of late years it has been.

found possible to treat the casein objects in a chemical bath to obtain. the desired polish and finish and thus not only improve the finalcasein objects, but reduce the cost of the polishing procchemical polish.

ess and the time required therefor, to a very large extent. The principle of the chemical polish is well known in the industry and there are a number of these chemical polishing compounds regularly sold on the market. 7 In'general the chemical finishing and polishing substancesconsist of an alkali hypochlorite or a mixture of several alkali hypochlorites, oran alkaline earth hypochlorite, or mixtures of various alkali and alkaline earth hypochlorites and such products will be referred to for the purpose of'this case as I have found that-there is a considerable variation in these chemical finishing compounds as to speed of reaction, strength of solution and therefore variations in the finished chemically polished casein objects. The usual procedure heretofore in factory practice for chemically-polishing caseinobjects has been as follows:- I V To 150 parts of water by weight, there is added 25 parts by weight of commercial chemical polish (i. e. hypochlorite solution containing about 47 to 51 grams of available chlorine per liter). Casein plastic objects are added to this hotsolution and are agitated therein by .any convenient means for about 4 minutes. 7 vThey are then-well washed, preferably several times (e. g. three times) with hot water, at about 140 F. to 150F; The objects are .then dried by any convenient means, e. g; in the air or in low temperature drying tunnels, preferably while being agitated. After following this process it willbe noted that the casein objects which previous to the chemical polish'treatment, possessed a dull, unpolished surface, after the treatment possess I a shiny, smooth, gloss-like'finish.

I have discovered however, that there are several serious defects resulting from the above method of chemically polishing casein objects. One objection is that after the' above described treatment the objects come out of the final wash water in rather a slightly sticky condition so that the objects are apt to stick together. They have rather a soft slimy feel. Furthermore, the most serious disadvantage by using this process resides in the fact that this chemicalpolish treatment often changes the shade of the casein objects.

And not only is thischanging of shade a serious drawback but it is still more serious from the fact that different batches of casein objects, buttons for example, which have been treated by this chemical polish, will not all be exactly the same shade, or do not preciselymatch the color shade desired. I have noticed in making five different batches of chemically polished brown buttons, the buttons having been dyed with the same brown anilinedye during the process of making the casein buttons, and applied in the same way, under like conditions, that the shade in each of the five batches was difierent'. I'believe that the reason for this is the factthat very slight changes intemperature of the solution of the chemical polish, or a slight difference in the length of time in which the buttons were immersed in the chemical polish solution, or a slight difference in the final washing of the different finished batches, may be the cause of this variation in shade. It can be well understood that such variations in shade of different batches in the same lot of buttons of casein objects, is a very serious matter and in many cases would compel one to place these various batches of off-shade finished buttons into another shade class, or to dispose of them as seconds or to re-dye these buttons, because of this non-uniformity.

My invention consists in a subsequent treat ment of the chemically polished casein objects (polished in hypochlorite solution) in such a manner that even though the shades up to the point of the casein objects having been chemi cally treated and washed, are varied, yet by my process I can bring them back to the original shade of color so that they will then be all of the original or'substantially original shade that they had prior to the chemical polishing treatment. To accomplish this improvement in the art of chemically polishing casein objects I give iii.

tens or casein objects in a weak, hot acid solution and allow these buttons or casein objects to remain in this solution for a few minutes, preferably with agitation. They are then removed and washed preferably in two washwaters, the water being at a temperature of about 140 F., removed.

from the wash water, drained and dried by the usual method. By this process I find that these.

buttons or casein objects will regain the exact shade or substantially the exact shade which theyv possessed prior to'having given them the chem.- ical polish treatment and furthermore when the buttons or casein objects are treated by my,

method they have a brighter, clearer'appearance than those not so treated, but treated by the usual: chemical polishing treatment.-

I have carried on 'a great many experiments with various types and kinds of acids and at various strengths and I have also made many tests with other organic and inorganic chemical compounds including many acid salts and/or alkali-neutralizing salts, and I find that what seems to be the most desirable and cheapest and yet highly effective way to accomplish these results is with a weak solution of an inorganic acid, although I am able to obtain quite satisfactory results with various organic'acids, but the time required to accomplish the results seems to be :longerthan with the mineral acids; I have also found that a number of the acid salts give quite satisfactory results.

In practicing this invention 1 do not wish to limit myself to any particular strength of acid or acid salts, although I have found very satisfactory results are obtained with very weak solutions. In order that one skilled in the art may practice my invention I give herewith one typical commercial example as to the method that can be followed:--

' Example 1 Into a proper tank, tub or mixer, I add 150 gallons of water and 2 gallons of ordinary commercial sulfuric acid of about 93% strength. This acid solution is heated to 150 F. and I then put into the mixture. lbs. of casein buttons or other moulded or shaped casein objects (which have been polished by treatment in the above described hypochlorite treatment). The temperature is kept at approximately F. for say, 10 minutes, and the immersed objects are gently stirred or tumbled in this acid solution during the treatment. The buttons or casein objects are then removed and are thoroughly washed, preferably giving two washings with water at about 140 F., while agitating. The objects are then drained and dried and it will be noted that the buttons or casein objects thus treated have returned to theexact shade or substantially the exact shade of the material prior 'to the chemical polish (hypochlorite) treatment. It is also found to be possible to obtain about the same results acid may be used without departing from the object of this invention.

Other examples which have given satisfactory results are as follows:

Example 2 70%, and the ordinary commercial grade. Proceed as in Example 1.

Example 4 gallons water, 2 gallons 35% formic acid. Proceed as in Example 1. The final results are quite-satisfactory but the time required for the casein objects to remain in the acid bath is somewhat longer. A treatment for 15-20 minutes is recommended, when using formic'acid.

7 Example 5 150 gallons of water, 2' gallons glacial acetic acid; Proceed as in Example 1. The results are entirely satisfactory,'but the length of timerequired'in the acid bath is somewhat longer than in Example .1, 12 to 115 minutes being satisfactory.

Example 6' 150 gallons of' water, '2 gallons lactic acid 85% purity. The results are satisfactory" but the period required is somewhat longerthan in Example l. About the; same results are securedas in Example 5. Example 7 150 gallons water, 2 gallons hydrofluoric acid 30% strength. Results satisfactory but the time in the acid bath is somewhatlonger than in Example 1, say 15 minutes.

Example 150 gallons of water, 2 gallons hydrofluosilicic acid30%'strength. The results are satisfactory but the time in the acid bath was approximately twice as long as in Example 1.

In place of the acids mentioned in'the examples, other acids, acid salts or substances capable of neutralizing alkalies, can be used. For instance I may mention oxalic acid 1.3 to 2%, propionic acid 1.5 to 2.5%, potassium bisulphite or sodium bisulphite 1.5 to 3% tartaric acid 1.5 to 2.5% (applied for say 5 to 15 minutes) or other substances such as trichloracetic acid, barbituric acid, succinic acid, disodium' phosphate, mono- .calcium phosphate, potassium bitartrate, glycerol phosphoric acid, malic acid, ammonium persulphate,aluminium sulphate or chloride, can also be employed, but in somewhat greater concentration 7 than given above, and/or continuing for a longer time; Ferric sulphate was found to restore the color rapidly, but gave a somewhat dull finish.

The process is applicable not only to casein products containing anilin dyes, but also to a wide variety of other dyes. It will be understood'however that when using casein plastics containing 1, say

, aioaees a particular dye, it is advisable to ascertain the concentration of the acid or acid salt that is best suited for that particular dye. The concentrations given in the examples are based on soluble anilin dyes, and particularly acid dyes (mixed with the caseinbefore extrusion, if desired), or mixtures of these and other dyes. It is to be understood that concentrations, times, temperatures of the acid treating bath are not limited to the'details given in the examples. The concentrations here given are such as will give a good color restoration within a few minutes, and without any apparent injury to the articles treated. The temperatures of 140 to 150 F. are preferred, but the solutions will be operative even at room temperature, although much slower; In many instances, substantial restoration of the color could be secured in half the time stated above.

It should be noted that the change of color (during the hypochlorite treatment and acid treatment) referred to in this specification applies not only to casein objects which have been made with various water soluble dyes, but it also applies to casein objects which have been colored with pigments of various types, as well as to casein objects of a white type containing white pigments and to casein objects which contain no dye or no pigments, known as blond type.

Where casein buttons or casein objects are made white by mixing into the casein at the time the casein plastic is made, various white pigments and then preparing the casein objects from such finished casein plastics and polishing by means of a chemical polish, I find that these white casein objects assume a yellowish cast and where the casein plastics have been made without the addition of any pigment or dye and thus produces what is known as a blond casein object and such casein plastic is made into objects and chemically polished, I find that such objects take on a yellowish cast but when any subsequent acid treatment is given to the white or the blond casein objects, they resume their natural shade.

My invention involves a process of improving the chemical polish or chemical finish of casein plastic objects substantially as described in this specification, by treating said objects after chemically polishing, with a water soluble acid reacting substance capable of restoring the fading of color or change of color caused by the'chemical polishing process.

For testing this process, a variety of differently colored batches of discs, stamped out of a casein plastic sheet have been treated by this process. Ina particular series of tests, a casein plastic chocolate brown color.

sheet was used, in which the moistened rennet casein was well mixed with a dye mixture consisting of Leather brown EG, Nigrocene crystals and Cloth red B extra. The mixture was then extruded, pressed into a thin sheet and dried, and the discs stamped out, formalized and then treated with a sodium hypochlorite solution containing about 7% of available chlorine, for giving the -chemical polish. The action of this latter solutioncaused a decided reddening of the discs, which before that treatment were of a deep The treatment as described restored the original color.

It may be stated that acid dyes of all colors are generally suitable for giving the desired color to casein plastics. Certain basic dyes have also been used. For giving thedesired color, it is common to use a mixture of several difierent dyes.

I claim:--

1. A process of treating shaped casein plastics having a predetermined color, which comprises first polishing said articles by subjecting same to the action of a hypochlorite solution to, polish the same whereby the color is injured and the surface rendered slimy, and thereafter tothe action of a solution having aweak acidic reaction, to restore the color.

2. A process of treating shaped casein plastics having a predetermined color, which comprises first subjecting same to the action of a hypochlorite solution to polish the same, and thereafter subjecting the same to the action of a dilute mineral acid solution.

3. A process of treating shaped casein plastics having a predetermined color, which comprises first subjecting same tothe action of a hypochlorite solution to polish the same, and thereafter subjecting said articles to the action of a dilute organic acid solution.

4. A process of treating shaped casein plastics having a predetermined color, which comprises first subjecting same to the action of a hypochlorite solution to polish the same, whereby the surface becomes discolored, and thereafter subjecting said plastics to the action of a solution of an acid salt, whereby the color is restored.

5. A process of treating shaped casein plastics having a predetermined color, which comprises first subjecting same to the action of a hypochlorite solution to polish the same, whereby the surface becomes discolored, and thereafter subjecting said plastics to the action of dilute sulphuric acid, whereby the color is restored.

WILL E. VAWTER. 

